Avoid locking the DB when there are no subitems to insert

qwarc/__init__.py

@@ -307,8 +307,8 @@ class QWARC:
 		self._tasks = pending
 
 	async def _insert_subitems(self, item):
-		async with self.exclusive_db_lock() as cursor:
-			if item.childItems:
+		if item.childItems:
+			async with self.exclusive_db_lock() as cursor:
 				it = iter(item.childItems)
 				while True:
 					values = [(t, v, STATUS_TODO) for t, v in itertools.islice(it, 100000)]